In this study, we have constructed a new cavitation model for cold water by taking the main elementary processes in cavitation into account based on the moment method. Particularly, we have valued the modeling of inception/collapse and coalescence/break-up, which changes the number density of cavitation bubbles. The proposed model was implemented to a CCUP (Cubic interpolation propagation - Combined Unified Procedure) flow solver where compressibility of liquid-vapor two-phase flow can be incorporated, and the validation was performed in a specific condition around a hydrofoil of NACA0015. As a result, it was confirmed that the new model can reproduce the cavitation inception/collapse rate and coalescence/break-up rate around the hydrofoil, at least qualitatively. On the other hand, the present model could not reproduce a large-scale characteristic unsteady phenomenon such as “cloud cavity shedding”. One of the reasons is that the present cavitation model was constructed based on the bubble physics at low void fractions, which cannot be simply applied to the higher void fractions, and this defect should be improved in the near future.

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In this study, fluid analysis at junction points for double Y type micro-channel two phase flow is carried out based on stabilized bubble function finite element method. This chip is widely applicable when we compound a medicine, or carry out environmental analysis, or make emulsions for cosmetics. In case that environmental analysis is carried out by using micro chemical chip, we have to completely devied two phase flow in micro channel. Hence, it is important to know the interface position based on numerical simulations before experiments and applications. In this study, incompressible Navier-Stokes equation with CFS model and continuity equation are employed to express flow fields, and advection equation is applied to compute the interface position. The finite element method is applied to compute these equations, and stabilized bubble function element is employed for discretization in space. In addition, fractional step method is applied to compute flow field. In this study, fluid analysis near Y junction for upstream and downstream sides are carried out. To confirm varidy of numerical results, those are compared with measurement results.

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Since a stepped circular cylinder is composed of two cylinders of different diameters, two different vortex shedding frequencies are presented in the wake. In the wake of a stepped circular cylinder, a pair of longitudinal vortices is formed behind the step. From spectral analysis, the longitudinal vortices are found to fluctuate with time at the frequency equal to the difference of the two vortex shedding frequencies. In this experiment, time variation of the flow field behind the stepped circular cylinder was investigated by phase ensemble averaging technique by means of X type hot wire anemometer. Pressure transducers are installed in the each cylinder part of different diameter, and their signals are digitally mixed and digitally filtered to produce an signal fluctuates at difference of the two vortex shedding frequencies, and it is used as reference signal of the phase ensemble averaging. From results of the experiments, velocity vector distributions in the plane perpendicular to the mean stream direction at the downstream of the stepped circular cylinder were found to vary drastically with time, and the strength of the longitudinal vortices was also found to vary periodically with time at the difference of the two vortex shedding frequencies. Furthermore, from TSC analysis of velocity signal obtained by means of I type hotwire anemometer, nonlinear interaction between two vortex shedding frequencies was detected around the longitudinal vortices.

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In order to calculate aerodynamic noise radiated from a complex-shaped body such as a pantograph of Shinkansen, an algorithm of the boundary element method for solving shape-adapted Green's functions is parallelized. The dense matrix of pluralistic simultaneous linear equations is divided and reallocated artfully on local memories assigned to each CPU of a massively parallel computer, which enable to handle numerical models with a large number of boundary elements. After modification, bench mark tests demonstrate high parallel performance with hundreds of processes. Then incompressible flow around the pantograph is calculated by the large eddy simulation (LES), and its results are coupled with shape-adapted Green's functions to evaluate aerodynamic noise based on formulas of vortex sound theory. By extracting the net contribution from diffracted and scatted sound sources that are distributed downstream of shafts and covers, sound pressure in the far field proves to agree well with wind tunnel experimental data.

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Japanese cedar (Cryptomeria japonica) pollinosis is the most common allergic diseases in Japan, and some researchers show about 26.5% of population being affected. Japanese cedar pollen is carried by the wind, but the pollen suspension transport behavior must be different from the wind (carrier air flow) behavior because the aerodynamic diameter of this pollen is relatively large. I estimate the mean aerodynamic diameter of Japanese cedar pollen as about 35μm in this study. The pollen falls when the wind is weak, and it is blown up and carried (saltation and resuspension) by the strong wind. If the pollen flow behavior was completely corresponding to the wind, the range of Japanese cedar growth would be very broad and the peculiar distribution of Japanese cedar might be confused. This study aims to clarify the cedar pollen suspension transport behavior and saltation transport mechanism, and to confirm the prediction method of this behavior and mechanism. Accordingly, the followings were done : (1) The aerodynamic diameter of Japanese cedar pollen was measured and the test particle was selected. (2) The suspension and saltation behavior of the test particle was observed and measured by the optical measurement methods. (3) The suspension and saltation behavior was also numerically calculated. These measured and calculated results are shown and evaluated by each other result in this paper. The knowledge about the relation between air and particle velocities is acquired. The saltation mechanism is cleared. The suspension and saltation transport behavior can be predicted by this study method.

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The interface between the turbulent and non-turbulent region in a two-dimensional turbulent jet is investigated by the simultaneous measurement of velocity and pressure. The measurements are performed using a combined probe comprising an X-type hot-wire probe and a static pressure probe. The measurement data are analyzed by the conditional sampling technique and an ensemble averaging technique on the basis of the intermittency function for the turbulent/non-turbulent decision. The measurement results at the cross-streamwise edge of the turbulent region show that there is a thin interfacial layer associated with a sharp jump of physical quantities (such as mean streamwise velocity) at the cross-streamwise edge of the turbulent region, and the thickness of interfacial layer is found to be 0.08 times the half-width of the cross-streamwise profile of the mean streamwise velocity. Moreover, the possibilities that there are small vortices in the middle of the interfacial layers and the existence of these vortices contributes to the transport of fluctuation pressure to the non-turbulent region are shown.

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We attempted to improve accuracy of particle image velocimetry (PIV) analysis using cross correlation function by introducing method to interpolate the brightness distribution of the measurement images. The motivation of introduction of the interpolation is that uncertainty included in the measurement result may be decreased by introduction of a certain interpolation method. The Fourier interpolation was introduced as the interpolation method focused on that the brightness distribution of a particle can be well approximated by the Gaussian profile, and Fourier transform of the Gaussian profile is equal to the exponential function. Specifically, the sine-function interpolation, which is a kind of the Fourier interpolation, was used, because the brightness distribution is not periodic. The effects of interpolation were investigated by a numerical simulation using quasi particle-images. Parameters in the simulation are moving distance, the particle diameter and the camera noise. This analysis showed that introduction of the interpolation can decrease uncertainty included in the PIV result.

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Pressure-sensitive paint (PSP) is a useful measurement technique to non-intrusively obtain a pressure distribution on a surface. Recently, PSP has been applied to micro gas flow measurements; thus the spatial resolution of PSP measurement is very important to assess the measured pressure. However, the spatial resolution has not been discussed except by Moshasrov et al. (1997). They evaluated the spatial resolution corresponds to a pressure jump on a PSP surface with consideration of an oxygen concentration distribution in a PSP layer. In this study, we have discussed the spatial resolution by numerically solving the two-dimensional diffuse equation with pressure slope as a boundary condition on a surface of PSP. The result with pressure jump, as a limiting case of pressure slope, showed good agreement with the result reported by Moshasrov et al. (1997). Moreover, it is theoretically clarified that the pressure variation with a spatial distance of lager than 8.5 times of the thickness of PSP can be completely measured by PSP without the effect of oxygen diffusion in a PSP layer.

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Superheated steam-containing hot air under atmospheric pressure has been used as a heating media for thermal processing such as food processing, cooking, sterilization, drying, and waste treatment. For these types of thermal processing, the steam mole fraction of the media sometimes strongly influences product quality. Hence, a simple method is required for measuring the steam mole fraction under a high temperature of more than 250°C. In this report, we propose an equation to calculate the steam mole fraction using the adiabatic saturation temperature for a wide range of temperatures and humidity values, i.e., from room temperature to 350°C and from room air to pure superheated steam. We also present a psychrometric chart with the steam mole fraction on the y-axis, which can indicate the presence of dry air and pure superheated steam. The values calculated by the proposed equation were in good agreement with values obtained in previous literature under comparable conditions. For developing a simple and convenient measurement method, a wet spherical gauze/brick is used for measuring the wet-bulb temperature. Its accuracy and applicability are investigated experimentally. The results show that this method can measure the steam mole fraction with an accuracy of less than 0.09 in the temperature range of 160-280°C. The causes of error and the methods for intending utilization are also investigated.

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Mathematical description of biological processes, including cell growth, cell differentiation, cell response to stress, and cell damage and death could be beneficial to the characterization, quantitative evaluation, design and optimization of the relevant processes. In this study, a mathematical model with reaction kinetic formulation was proposed and developed to describe the process of cell differentiation with cell growth. Basic equations and analytical solutions for the numbers of undifferentiated and differentiated cells were obtained. A parameter study of the model constants, rate constants of cell growth and differentiation, was performed to analyze the model characteristics. An experiment with a rat pheochromocytoma cell line PC12 as nerve cells was also performed to evaluate time-series changes in the numbers of undifferentiated and differentiated cells. The rate constants were determined by inverse problem analysis based on the experiment with PC12 cells. The prediction by the model well simulated the characteristics of the experiment, proving that the present reaction kinetic model successfully represents cell differentiation with cell growth. Therefore, the cell growth and differentiation can be appropriately characterized by the rate constants, regarded as specific characteristics of cells.

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